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From: gshipman (gshipman_at_[hidden])
Date: 2007-04-26 16:28:33


There is a known issue on BProc 4 w.r.t. pty support. Open MPI by
default will try to use ptys for I/O forwarding but will revert to
pipes if ptys are not available.

You can "safely" ignore the pty warnings, or you may want to rerun
configure and add:
--disable-pty-support

I say "safely" because my understanding is that some I/O data may be
lost if pipes are used during abnormal termination.

Alternatively you might try getting pty support working, you need to
configure ptys on the backend nodes.
You can then try the following code to test if it is working
correctly, if this fails (it does on our BProc 4 cluster) you
shouldn't use ptys on BProc.

#include <pty.h>
#include <utmp.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

int
main(int argc, char *agrv[])
{
   int amaster, aslave;

   if (openpty(&amaster, &aslave, NULL, NULL, NULL) < 0) {
     printf("openpty() failed with errno = %d, %s\n", errno, strerror
(errno));
   } else {
     printf("openpty() succeeded\n");
   }

   return 0;
}

On Apr 26, 2007, at 2:06 PM, Daniel Gruner wrote:

> Hi
>
> I have been testing OpenMPI 1.2, and now 1.2.1, on several BProc-
> based clusters, and I have found some problems/issues. All my
> clusters have standard ethernet interconnects, either 100Base/T or
> Gigabit, on standard switches.
>
> The clusters are all running Clustermatic 5 (BProc 4.x), and range
> from 32-bit Athlon, to 32-bit Xeon, to 64-bit Opteron. In all cases
> the same problems occur, identically. I attach here the results
> from "ompi_info --all" and the config.log, for my latest build on
> an Opteron cluster, using the Pathscale compilers. I had exactly
> the same problems when using the vanilla GNU compilers.
>
> Now for a description of the problem:
>
> When running an mpi code (cpi.c, from the standard mpi examples, also
> attached), using the mpirun defaults (e.g. -byslot), with a single
> process:
>
> sonoma:dgruner{134}> mpirun -n 1 ./cpip
> [n17:30019] odls_bproc: openpty failed, using pipes instead
> Process 0 on n17
> pi is approximately 3.1415926544231341, Error is 0.0000000008333410
> wall clock time = 0.000199
>
> However, if one tries to run more than one process, this bombs:
>
> sonoma:dgruner{134}> mpirun -n 2 ./cpip
> .
> .
> .
> [n21:30029] OOB: Connection to HNP lost
> [n21:30029] OOB: Connection to HNP lost
> [n21:30029] OOB: Connection to HNP lost
> [n21:30029] OOB: Connection to HNP lost
> [n21:30029] OOB: Connection to HNP lost
> [n21:30029] OOB: Connection to HNP lost
> .
> . ad infinitum
>
> If one uses de option "-bynode", things work:
>
> sonoma:dgruner{145}> mpirun -bynode -n 2 ./cpip
> [n17:30055] odls_bproc: openpty failed, using pipes instead
> Process 0 on n17
> Process 1 on n21
> pi is approximately 3.1415926544231318, Error is 0.0000000008333387
> wall clock time = 0.010375
>
>
> Note that there is always the message about "openpty failed, using
> pipes instead".
>
> If I run more processes (on my 3-node cluster, with 2 cpus per
> node), the
> openpty message appears repeatedly for the first node:
>
> sonoma:dgruner{146}> mpirun -bynode -n 6 ./cpip
> [n17:30061] odls_bproc: openpty failed, using pipes instead
> [n17:30061] odls_bproc: openpty failed, using pipes instead
> Process 0 on n17
> Process 2 on n49
> Process 1 on n21
> Process 5 on n49
> Process 3 on n17
> Process 4 on n21
> pi is approximately 3.1415926544231239, Error is 0.0000000008333307
> wall clock time = 0.050332
>
>
> Should I worry about the openpty failure? I suspect that
> communications
> may be slower this way. Using the -byslot option always fails, so
> this
> is a bug. The same occurs for all the codes that I have tried,
> both simple
> and complex.
>
> Thanks for your attention to this.
> Regards,
> Daniel
> --
>
> Dr. Daniel Gruner dgruner_at_[hidden]
> Dept. of Chemistry daniel.gruner_at_[hidden]
> University of Toronto phone: (416)-978-8689
> 80 St. George Street fax: (416)-978-5325
> Toronto, ON M5S 3H6, Canada finger for PGP public key
> <cpi.c.gz>
> <config.log.gz>
> <ompiinfo.gz>
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